The load rejection test of the steam turbine unit is one of the important tests that must be completed in the infrastructure commissioning phase required by the Ministry of Electric Power for the “Start-up and Completion Acceptance Regulations for Thermal Power Plantsâ€. The main purpose is to evaluate the dynamic characteristics of the steam turbine regulation system. The steam turbine load rejection test is to directly disconnect the generator main oil switch, switch the plant power supply to the standby power supply, disassemble the unit and the power grid, and remove all the electric load. The steam turbine maintains stable operation at 3 000 r/min. In order to adapt to the stability and safety requirements of the power system, in the large steam turbine group, the operating conditions of the FCB (FCB is FASTCUT BACK) are designed. The main purpose is to disassemble the unit from the grid after the unit grid fails and load. Under automatic control, the operation of the turbine island is maintained (that is, the generator set load is self-contained), the boiler maintains the minimum combustion load, and the host bypass system automatically maintains the parameters of the unit operation. After the grid is restored, the unit can be directly connected to the grid. Running with load. However, due to various reasons, the test success rate of the unit island operation mode is very low, and the No.1 and No.2 units of Hejin Power Plant successfully carried out the steam turbine island test 1 unit after completing the 168h trial operation and the conventional load rejection test. Overview The first 350MW coal-fired units of the first phase of the Hejin Power Plant will be introduced to Japan's Mitsubishi equipment, equipped with a 1205T/H-MB-FRR single steam drum manufactured by Mitsubishi Heavy Industries, radiation, reheat, square corner, forced circulation open-air boiler, and TC2F-35.4" Subcritical, a middle-level university of thermal power, engineer; Guo Jian (1963-), male, Shanxi Taiyuan, graduated from the Taiyuan University of Technology Electric Power Branch in 1986, senior engineer; Duan Chengqun see this journal This is the 52nd page.
Reheating, reaction type single-shaft double-cylinder double-row steam condensing steam turbine and MB-J horizontal all-hydrogen internal cooling, hidden pole full static thyristor rectifier excitation generator-transformer unit wiring manufactured by Mitsubishi Electric, Connected to the system control system with 220kV voltage level for DCS manufactured by Mitsubishi Heavy Industries, model DIASYS-JP/V functions including DAS, CCS, MT-3EH, BF-DEH, BMS, GWC turbine bypass system using high and low voltage series two stages The bypass unit has a capacity of 40% of the total flow, and the bypass regulating valve is produced by CCI Corporation of the United States. The high and medium pressure steam turbines are composed of impulse and reaction type. Two steam chambers are arranged symmetrically on both sides of the high and medium pressure cylinders. Each steam chamber includes a main steam valve and two high pressure regulating valve medium pressure main steam valves and medium pressure regulating valves. Medium pressure combined valve.
The adjustment system of the steam turbine adopts the digital electro-hydraulic control system (ie DEH). The adjustment system of the steam turbine includes three parts: the speed measuring component amplifying component and the actuator. After the rotor is closed, the negative speed feedback is automatically adjusted. The Mitsubishi unit uses a 2.5MPa pressure turbine oil as the power pool for the control system. The DEH is equipped with multiple sets of microcomputer systems. It is the subsystem of the multi-stage distributed computer control system. The DEH is distributed through the distributed control system communication network and the unit. The system transmits signals to make the operation of the DEH integral with the control of the whole unit. The output control signal of the DEH is controlled by “3 taking 2* logic or median, then driving the electro-hydraulic converter, performing the adjustment function 2 and the conventional load rejection test according to The requirements of the Ministry of Electric Power "Procedures for the Start-up and Completion Acceptance of Thermal Power Plants" were carried out before the trial operation of No.1 and No.2 units of Hejin Power Plant, 50%, 75%, 100% of the conventional load before the trial operation. Test, because the conventional method of load rejection test is carried out in the infrastructure commissioning unit, and the success of the load shedding table 1 No. 1 and No. 2 unit 甩 100% rated load test record item before the load load parameter after the load test peak load / MW/1 No. 02 action once, action time action once, action time 0.032s1 high pressure adjustment door 1001000 off time 290ms0 off time 290ms2 high pressure Adjustment door 1001000 off time 290ms0 off time 290ms3 high pressure adjustment door 27.522.50 off time 120ms0 off time 120ms4 high pressure adjustment door 1100 left middle pressure adjustment door 10010000 off time 191 off time 192 right side medium pressure adjustment door 10010000 off time 191 off time 192 rate Close to 100%; so there is no more description here. The main parameters of the two units of the conventional method of load rejection test 1 through the test, the dynamic characteristics of the adjustment system of the two units fully meet the acceptance requirements 3 unit load-breaking island operation (FCB test) The FCB test is a relatively large, complex and risky severe disturbance test involving all majors of the steam turbine boiler, electrical, thermal and power plants and all parts of the plant. The success or failure of the FCB test will directly affect The operation mode of the island and the switching of the plant power consumption, etc., the test is carried out after the test plan and the safety measures have been repeatedly demonstrated, approved by the leading group, and the personnel involved in the test are fully technically delivered.
3.1 Pre-test and system check The static test of the main valve and the speed-regulating valve closing time is qualified; the main valve and the door-adjusting activity test are qualified, and the extraction check valve activity test is qualified; the ESC system can meet the system start and stop. And lifting load requirements; the main valve and speed control valve tightness test of the unit is qualified; the RB test is completed, the test is all qualified, the auxiliary machine system is running well; the load is increased or decreased; the boiler combustion system, the plant power fast cutting system, the power generation The excitation system of the excitation system and the standby branch power supply of the thermal control system are operating normally, and the turbine generator set is viable. The main process of the small island operation test of the No. 3.21 steam turbine unit was carried out on the island on January 14, 2001 after the trial operation. After the completion of the preliminary test and the system check, the test personnel participated in the technical delivery, and each of them was at 15:37:27 in the afternoon. The general commander carried out a 10s countdown, and manually removed the generator main oil switch at 15:37:37. 52G, FCB action, the electric load reached 18.5MW, and the unit maintained the operation of the island. The main process of cutting the unit from the coordinated operation mode to the manual operation of the machine is as follows.
Grinding the main control is an automatic backup mode, maintaining the grinding operation at a minimum load of 20t / h, the CD layer oil gun is automatically put into, the fuel flow is controlled by 7. / h control OPC action; the machine front pressure 17. 3MPa, 2 main steam safety doors PCV1 and PCV2 are active.
4 high-profile doors GV Bu GV4 and 2 medium-voltage control ICV1, ICV2 full-off 2 high-pressure adjustment doors and 2 medium-voltage adjustment doors start to open.
37 minutes and 55 seconds high and low side pressure regulating valve release the full opening command by itself, and resume automatic adjustment mode 39 minutes and 46 seconds. Adopt GOV mode manual grid connection, 52G re-close the unit cutting furnace to follow the power adjustment mode: high side adjustment main steam Pressure, the machine master is the GOV power control in the ESC mode. But at this time, the electric load instantaneously dropped to 4. 9MW. This is because when the grid is connected, the turbine speed is only 2990r/min, which causes the generator to reverse power protection action. It is only because the machine main control command is quickly added and the door is opened. 52G once again tripped for 40 minutes and 38 seconds. Because the water level of the steam drum fluctuated greatly, the high side cut was manually operated and forced to 20%. The coordinated cutting was followed by the machine. The electric load was 40 minutes and 42 seconds. The FCB was automatically reset, and the boiler was controlled and milled. Both the coal machine main control and the fuel main control are cut manually. Trying to add boiler load command to increase the electric load, but because the load is controlled in the ESV circuit, it is invalid. 1g) The unit can be set negative in various control modes. The load curve her shingjkU0%3* high side-by-side automatic, coordinated and cut into the furnace to follow the power adjustment mode, the electric load 12. The machine main control cuts to the ESC control mode, manually adjusts the door opening degree.
The pressure reducing valve is fully closed. After 6s, the high pressure is given to the main control and the main control is automatically injected. The unit cuts the coordinated control mode and the rated power suddenly loads the load to the plant and re-establishes the grid and quickly loads the steam turbine rotor. The thermal stress change is a special consideration. From the data provided by Mitsubishi, the direct shadow table 2 first test data record value initial value maximum value minimum value final value unit load / MW35835814. Table 3 second test data Record value initial value maximum value minimum value final value unit load / MW / 349. 3.32 unit island operation test based on the success of unit 1 test, we at 22:57 on March 23, 2001 in unit 2 In the first FCB test, the high side was opened smoothly, but due to the MFT action of the whole furnace fire extinguishing, the test failed. After the analysis by all parties, it was considered that the fuel command of the grinding master fell too fast (300t/min). In the FCB test, the rate is 25t/min. For this reason, the 300t/min of the No. 2 machine is changed to 8t/min. After a large number of preparatory work, the second test and system check are carried out, and then the test is carried out. Personnel performing technology After the delivery, the general commander will carry out the 10s countdown. At 9:10:10, the generator main oil switch 52G will be manually pulled out, the FCB will operate, and the electric load will reach 13.7MW, with the plant power island running. The unit was cut into the machine by the coordinated operation mode, and the manual mode of the furnace was the same as that of the No. 1 unit. The test of Unit 2 was very successful.
The test data is shown in Table 3. 4 Conclusion Modern large-scale steam turbines fully apply thermal stress to control the life of the rotor. Therefore, the temperature of the rotor after FCB becomes an important judgment factor for the speed of the unit's grid connection. Most turbo generators The equipment is designed to withstand a period of time and is completely separated from the system and operates without load or on-board power. When the temperature of the first stage is immediately decreased by about 120*C, and then the superheater outlet temperature is adjusted to the newly established steam parameter level within 15 minutes, the steam temperature of the first stage is further decreased by 90 °C. A peak stress will be generated within 10 minutes to 15 minutes after the start of the transient, and the stress will slowly decay to zero within about 1 hour. If the plant power is kept for a long time, the rotor will be forced to cool to a new equilibrium state and then should be moderate. Rate complete reloading to avoid large stresses in the opposite direction. For a typical 3000r/min rotor, the peak stress may cause initial cracks in the rotor after the stress has completely changed from 100 to 400 cycles. Therefore, it can be calculated This cycle of the order of magnitude is about the total fatigue performance of the rotor. It can be seen that it is very important to realize the FCB function of the unit. However, the damage to the unit equipment under such conditions for a long time is very obvious. Although the load test can test the dynamic characteristics of the steam turbine control system, in normal operation, the unit may suddenly drop the load at any time. If the power supply is not put into time, the auxiliary machine will be shut down. If the operator is not properly handled, it is very likely that the operating parameters will be exceeded. This will cause major accidents such as large shaft bending and bearing bushing. If the unit island operation mode is realized and promoted, it can avoid similar. The occurrence of the incident is also very helpful for the safe operation of the power plant.
FCB island operation is a very effective operation mode for large steam turbines to adapt to grid changes. In this way, if the steam turbine group can quickly connect to the grid for power generation in a short period of time, the safe and economic operation of the unit and the safety of the grid. Stable operation is of great significance. It should be a necessary operation of a modern unit. The relative difference between the results of the operation should be less than the relative expansion uncertainty of the device. The verification data of the two sets of devices are verified. See Table 2, Table 2, two sets of devices. The comparison result (the added voltage 5000 table 4 two sets of device comparison results show value Beijing Institute of Electric Power / G device G relative difference /% allowable value%100M100.12100.102 <10-47 through the above argument, combination The high-pressure and high-resistance box verification device is practical and feasible in the actual verification work. It is stable and reliable. The measurement range is Kfn-10na, which can meet the verification of most high-pressure high-resistance boxes.
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